The present application relates generally to sensors adapted to detect optical or ionizing radiation, and more specifically to multi-layer amorphous selenium (a-Se) sensors and their methods of production.
Amorphous selenium (a-Se) has been commercialized both as an optical sensor and direct x-ray detector, and a-Se with avalanche gain has also been proposed for use in an indirect x-ray detector. Advantages of a-Se over other photoconductors such as silicon, which may be used in both optical and x-ray sensing applications, and CdTe, which may be used to detect x-rays, include the capability for large area deposition, avalanche multiplication of holes at electric fields (ESe) greater than 70 V/um, and monotonically increasing x-ray conversion gain with ESe.
As will be appreciated, conventional x-ray detectors, especially x-ray detectors adapted for low photon flux applications, suffer from image degradation due to electronic noise. However, decreasing the electronic noise of readout electronics increases the cost of the imager and has limited effect.
On the other hand, for a-Se detectors electronic noise can be overcome by increasing ESe to amplify the signal prior to the introduction of electronic noise. For optical sensors, ESe greater than 70 V/um is required for avalanche gain, while for direct x-ray sensors any increase in ESe will increase conversion gain.